Immunity to Flu May be Inhibited by Obesity

Obesity has been shown to have many adverse health effects, including an increased susceptibility to infection. The CDC has listed obesity as a risk factor for pandemic flu strains, such as the H1N1 virus. In new research using laboratory mice, scientists from the University of North Carolina at Chapel Hill have found that obesity may limit the body’s ability to fight infection, but may also decrease its ability to develop immunity against secondary influenza viruses.

The nutrition researchers from the UNC Gillings School of Global Public Health infected both lean and obese mice with a mild influenza virus. When the mice recovered from the first bout of flu, they were re-infected with a larger dose of a more lethal strain. Twenty-five percent of the obese mice died, but all of the lean mice survived.

Erik Karlsson, doctoral candidate in nutrition and lead author of the study, and his team found that the obese mice were not able to develop a protective influenza-specific memory T-cell which are generated by the body during an initial influenza infection and protect against a second infection.

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Although similar in theory to the response an individual receives to a flu vaccine, this research shows that memory T-cells would target internal proteins common to all strains of influenza virus while the vaccine is specific to one strain.

Previous hypotheses for the link between obesity and higher risk for infection included the chronic inflammatory state caused by excess adipose tissue which affects the immune response. In 2007, researchers from Boston University found that obese mice were not as effective in combating infection due to the reduced immune system response. That research was published in the December issue of the Proceedings of the National Academy of Sciences.

Dr. Melinda Beck PhD, professor of nutrition at UNC, collaborated on this study which builds on her previous work published in the Journal of Nutrition in 2007. There she found that obese mice had a significantly higher mortality rate with a primary influenza infection.

The research is published in the March 15 issue of The Journal of Immunology.

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